Sheet discharge apparatus and image forming apparatus

ABSTRACT

A sheet discharge apparatus includes: a discharger that discharges a sheet; a loading part on which the sheet discharged from the discharger is loaded; an abutment member that abuts against a rear end of the sheet in a direction of discharging to align the sheet loaded on the loading part; a pull-back member that performs a pull-back operation by contacting with the sheet discharged from the discharger to pull back the sheet toward the abutment member; and a hardware processor that controls the pull-back member. The hardware processor performs the pull-pack operation on a sheet bundle when determining that the sheet bundle bound by a binder is discharged from the discharger.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. § 119 to Japanese patent Application Nos. 2018-075429, 2018-075430, 2018-075431, and 2018-075432, all filed on Apr. 10, 2018. The contents of these applications are incorporated herein by reference in its entirety.

BACKGROUND Technological Field

The present invention relates to a sheet discharge apparatus and an image forming apparatus.

Description of the Related Art

Conventionally, an image forming apparatus and a sheet processor are provided with a sheet discharge apparatus for discharging a sheet subjected to predetermined processing. The sheet discharge apparatus mainly includes a discharger that discharges a sheet, and a loading part that loads the sheet discharged from the discharger. A sheet discharged from the discharger falls by its own weight and is sequentially stacked on the loading part. The loading part has an inclined shape such that a rear end side of a sheet faces downward with reference to a discharge direction of the sheet by the discharger. An abutment plate is disposed at an end portion of the loading part corresponding to a rear end side of a sheet. A sheet that has fallen to the loading part slides down a top surface of the loading part (or a top surface of the uppermost sheet) and is aligned by abutting against the abutment plate.

For example, JP 2011-105440 A discloses a sheet discharge apparatus in which a sheet alignment state of sheets loaded on a loading part is improved. This sheet discharge apparatus has a sheet-loading unit and a sheet grip member. Here, the sheet-loading unit includes a loading part that loads a sheet discharged by the discharger, and a sheet rear end abutment part to which a rear end in a sheet conveyance direction when a sheet is discharged by the discharger abuts. Meanwhile, the sheet grip member grips a sheet discharged from the discharger at a sheet grip position, and grips and moves the sheet until the sheet is loaded on the loading part. When the sheet grip member reaches a sheet-loading position, the sheet grip member is moved in a direction opposite to the sheet conveyance direction, and the rear end of the sheet to be gripped abuts against the sheet rear end abutment part. Similar technologies are also disclosed, for example, in JP 2013-100169 A and JP 2013-151345 A.

Meanwhile, in a sheet discharge apparatus, there is a case where a sheet bundle bound by a binder is handled. In this sheet bundle, when the sheet bundle discharged from the discharger slides down a top surface of an uppermost sheet bundle loaded on a sheet tray, the each binder sometimes gets caught. Therefore, there is a possibility that the rear end of the discharged sheet bundle does not reach the abutment plate, and the sheet bundle is loaded unevenly.

SUMMARY

One or more embodiments of the present invention provide a sheet discharge apparatus and an image forming apparatus capable of orderly loading a sheet bundle bound by a binder.

According to one or more embodiments of the present invention, a sheet discharge apparatus comprises: a discharger that discharges a sheet; a loading part on which the sheet discharged from the discharger is loaded; an abutment member against which a rear end of the sheet based on a direction in which the sheet is discharged by the discharger abuts so as to align the sheet loaded on the loading part; a pull back member that performs pull back operation of contacting with the sheet discharged from the discharger to pull back the sheet toward the abutment member; and a hardware processor that controls the pull back member, wherein the hardware processor performs the pull back operation on a sheet bundle when determining that the sheet bundle bound by a binder is discharged from the discharger.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages and features provided by one or more embodiments of the invention will become more fully understood from the detailed description given hereinbelow and the appended drawings which are given by way of illustration only, and thus are not intended as a definition of the limits of the present invention:

FIG. 1 is a configuration diagram schematically showing an image forming apparatus according to one or more embodiments;

FIG. 2 is an enlarged explanatory view showing a main part of a sheet discharge apparatus according to one or more embodiments;

FIGS. 3A and 3B are explanatory views showing operation of an upper gripper and a lower gripper according to one or more embodiments;

FIGS. 4A and 4B are explanatory views showing operation of the upper gripper and the lower gripper according to one or more embodiments;

FIG. 5 is a flowchart showing operation of a gripper according to one or more embodiments;

FIG. 6 is a flowchart showing operation of a gripper according to one or more embodiments; and

FIG. 7 is an explanatory view showing a state of a sheet bundle loaded on a sheet tray.

DETAILED DESCRIPTION

Hereinafter, one or more embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the disclosed embodiments.

FIG. 1 is a configuration diagram schematically showing an image forming apparatus according to one or more embodiments. The image forming apparatus according to one or more embodiments includes an image forming apparatus main body 1 and a post-processing device 2.

The image forming apparatus main body 1 is an electrophotographic image forming apparatus such as a copying machine, and forms an image on a sheet P on the basis of image data. The image forming apparatus main body 1 includes a document reading device 5, a photoconductor 11, a charging part 12, an image exposure part 13, a developing part 14, a transfer part 15A, a separation part 15B, a cleaning device 16, a fixing device 18, and an image formation control part 19.

The document reading device 5 is disposed at the upper part of a housing of the image forming apparatus main body 1, and includes an automatic document feeding part for automatically moving a document when reading an image. The document reading device 5 reads an image formed on a document and outputs a predetermined image signal. The outputted image signal is created as image data by being subjected to A/D conversion.

An image reading control part (not shown) included in the document reading device 5 applies processing such as shading correction, dither processing, or compression to the image data, and data obtained by this processing is outputted as final image data to the image formation control part 19. In addition to acquiring image data from the document reading device 5, the image formation control part 19 may acquire image data from a personal computer or another image forming apparatus connected to the image forming apparatus.

A surface of the photoconductor 11 is uniformly charged by the charging part 12. The image exposure part 13 scans and exposes the surface of the photoconductor 11 with a laser beam on the basis of output information outputted from the image formation control part 19 on the basis of the image data. As a result, a latent image is formed on the surface of the photoconductor 11. The developing part 14 develops the latent image with toner and forms an image (toner image) on the surface of the photoconductor 11.

A sheet P accommodated in a sheet tray 17A is fed to the transfer part 15A. The transfer part 15A transfers the image on the surface of the photoconductor 11 to the sheet P. The separation part 15B separates the sheet P to which the image has been transferred from the photoconductor 11. The cleaning device 16 removes toner remaining on the surface of the photoconductor 11 after the image is transferred to the sheet P. An intermediate conveyance part 17B conveys the separated sheet P to the fixing device 18.

The fixing device 18 performs fixing processing for fixing the image on the sheet P by heating and pressing. A first discharge roller 17C discharges (supplies) the sheet P subjected to the fixing processing to the post-processing device 2.

On the other hand, when image formation is performed on both surfaces of the sheet P, the conveyance direction of the sheet P subjected to the fixing processing by the fixing device 18 is switched from the first discharge roller 17C side to the lower (reverse conveyance part 17E) side by a conveyance path switching plate 17D. The reverse conveyance part 17E reverses the front and back of the sheet P by switching back the sheet P, and then conveys the sheet P to the transfer part 15A.

The image formation control part 19 controls the image forming apparatus main body 1. As the image formation control part 19, a microcomputer mainly including a CPU, a ROM, a RAM, and an I/O interface can be used. The CPU performs various programs (processor). The ROM stores various programs to be performed by the CPU in the form of program codes readable by the CPU. The ROM stores data required for executing the program. The RAM is a memory serving as a work storage area. The program and the data stored in the ROM are read out by the CPU to be developed in the RAM. The CPU performs various processes on the basis of the program and data developed in the RAM.

The post-processing device 2 is disposed at the subsequent stage of the image forming apparatus main body 1 and is a sheet processor that performs predetermined processing (post-processing) on the sheet P discharged from the image forming apparatus main body 1. In the one or more embodiments, the post-processing device 2 performs stapling processing (binding processing), that is, processing of stacking a plurality of sheets P discharged from the image forming apparatus main body 1 and binding the plurality of sheets P by a staple (binder). The post-processing device 2 mainly includes an introduction part 20, an intermediate stacker 40, a staple part 45, a sheet discharge apparatus 50, and a post-processing control part (hardware processor) 70.

The introduction part 20 receives the sheet P discharged from the image forming apparatus main body 1, and sends the sheet P to the inside of the post-processing device 2. The position of the introduction part 20 is set so as to correspond to the first discharge roller 17C of the image forming apparatus main body 1.

In order to introduce the sheet P other than the sheet P discharged from the image forming apparatus main body 1 to the post-processing device 2, the post-processing device 2 is provided with a sheet supply unit 30. The sheet supply unit 30 includes a sheet feed tray 31 and a sheet feed part 32. The sheet P placed on the sheet feed tray 31 is taken in by the sheet feed part 32 and then is conveyed along a predetermined conveyance path to join the conveyance path downstream of the introduction part 20.

The outline of the conveyance path of the sheet P in the post-processing device 2 will be described. The conveyance path downstream of the introduction part 20 is branched into a first conveyance path R1, a second conveyance path R2, and a third conveyance path R3, and the sheet P from the introduction part 20 is conveyed through any of the conveyance paths R1 to R3 according to switching of a switching gate (not shown). When the sheet P is discharged to a tray outside the machine without performing the stapling processing, the switching gate is set to the first conveyance path R1 or the third conveyance path R3. On the other hand, when the stapling processing is performed, the switching gate is set to the second conveyance path R2.

The first conveyance path R1 is a path through which the sheet P sent from the introduction part 20 is conveyed as it is to the sheet discharge apparatus 50 without being subjected to any processing. In the first conveyance path R1, a conveyance roller or the like for conveying the sheet P is disposed.

The second conveyance path R2 is a path through which the sheet P sent from the introduction part 20 is conveyed via the intermediate stacker 40 to the sheet discharge apparatus 50. In the second conveyance path R2, a conveyance roller for conveying the sheet P, a stacker discharge roller 26, a conveyance belt 27, or the like are disposed.

The stacker discharge roller 26 is disposed at a position facing the sheet-loading surface of the intermediate stacker 40, and discharges the sheet P conveyed through the second conveyance path R2 to the intermediate stacker 40. The conveyance belt 27 conveys a sheet bundle loaded on the intermediate stacker 40, that is, a plurality of sheets P bound by the staple to the sheet discharge apparatus 50.

The intermediate stacker 40 sequentially loads the sheet P discharged from the stacker discharge roller 26 for the stapling processing by the staple part 45. The intermediate stacker 40 is disposed such that the tip end of the sheet P loaded on the intermediate stacker 40 is inclined so as to be higher than the rear end. When the sheet P discharged from the stacker discharge roller 26 falls onto the intermediate stacker 40, the sheet P slides down on the intermediate stacker 40, and the rear end portion of the sheet P abuts against a rear end guide plate (not shown) to stop moving.

The staple part 45 includes a stapler that puts a staple, and a clincher that bends a tip of the staple along the sheet P. This staple part 45 subjects a plurality of sheets P loaded on the intermediate stacker 40 to stapling in accordance with a predetermined position and orientation, thereby performing the stapling processing. For example, the staple part 45 performs end binding of stapling the rear end portion of the sheet P.

The third conveyance path R3 is a path through which the sheet P fed from the introduction part 20 is conveyed to a sub tray 60. A conveyance roller for conveying the sheet P is disposed in the third conveyance path R3. The sub tray 60 is disposed at the upper portion of the outside of the machine. Since the amount of sheets that can be loaded is small, the sub tray 60 is used for discharging a small amount of special sheets P such as thick sheets.

The sheet discharge apparatus 50 is a device that discharges and accumulates the sheet P conveyed in the post-processing device 2. In this specification, unless otherwise stated, the term “sheet P” is used as a concept including not only a single sheet P but also a sheet bundle bound by a staple. The sheet discharge apparatus 50 mainly includes a second discharge roller 51, a sheet tray (loading part) 52, a raising and lowering mechanism 53, an abutment plate 54, and a gripper (pull-back member) 55. Here, FIG. 2 is an explanatory view enlarging a main part of the sheet discharge apparatus 50.

The second discharge roller 51 is located at the end of each of the first conveyance path R1 and the second conveyance path R2, and discharges the conveyed sheet P in each of the conveyance paths R1, R2. In this specification, the front end and the rear end of the sheet P in the sheet discharge apparatus 50 are defined with reference to the discharge direction of the sheet P of discharging from the second discharge roller 51.

The sheet tray 52 is a tray on which the sheet P discharged from the second discharge roller 51 is loaded. The sheet tray 52 can be raised and lowered along the sheet-loading direction W1 by the raising and lowering mechanism 53 (see FIG. 1). The raising and lowering mechanism 53 is controlled by the post-processing control part 70 so that the uppermost sheet P loaded on the sheet tray 52 is maintained at a predetermined height.

The sheet tray 52 has a shape that is inclined such that the tip end side of the sheet P accumulated on the sheet tray 52 is higher than the rear end side. A vertical wall-shaped abutment plate 54 is provided on the rear end side of the sheet P in the sheet tray 52. The abutment plate 54 has a function of aligning the sheet P by abutment of the rear end of the sheet P accumulated on the sheet tray 52.

A gripper 55 contacts with each of both surfaces of the sheet P to grip the sheet P. The gripper 55 grips the rear end of the sheet P discharged from the second discharge roller 51 and performs pull back operation to pull back the sheet P in the direction of the abutment plate 54. The gripping of the sheet P by the gripper 55 is performed until the rear end of the sheet P falls on the sheet tray 52 (including the uppermost sheet P). The gripper 55 includes an upper gripper 56 that contacts with the upper surface side of the sheet P and a lower gripper 57 that contacts with the lower surface side of the sheet P.

FIGS. 3A and 3B and FIGS. 4A and 4B are explanatory views showing the operation of the upper gripper 56 and the lower gripper 57. The lower gripper 57 is connected to an actuator (not shown) via a link mechanism 57 a or the like. When the actuator is driven, the lower gripper 57 rotates while drawing the orbit indicated by a broken line in FIG. 2. Specifically, the position of the lower gripper 57 shown in FIG. 3A is a start position (grip start position) at which the sheet P discharged from the second discharge roller 51 is gripped together with the upper gripper 56. The lower gripper 57 moves from the grip start position to the lower right direction in the drawing along the orbit (FIG. 3B), and then reaches inside the abutment plate 54 (FIG. 4A). Then, the lower gripper 57 moves from this position in the upward direction in the drawing along the orbit, and moves to a standby position (FIG. 4B).

On the other hand, the upper gripper 56 is pivotally supported at the rear end side with respect to a bracket 56 a, and a tip end side of the upper gripper 56 swings around a rotation axis. A biasing member (not shown) such as a spring is provided in the upper gripper 56, and the tip end side thereof is biased so as to face downward in the drawing. The upper gripper 56 is pressed against the lower gripper 57 at the grip start position by the biasing force of the biasing member (FIG. 3A). By this pressing force, the sheet P can be gripped between the upper gripper 56 and the lower gripper 57.

When the lower gripper 57 rotates along the orbit, the upper gripper 56 swings so as to follow the rotation of the lower gripper 57 under the biasing force of the biasing member. Since the state of the upper gripper 56 being pressed against the lower gripper 57 is maintained, the sheet P remains sandwiched between the upper gripper 56 and the lower gripper 57. During the movement of the upper gripper 56 and the lower gripper 57, the rear end of the sheet P abuts against the abutment plate 54 (FIG. 3B).

When the rear end of the sheet P abuts against the abutment plate 54, the bracket 56 a coupled to the upper gripper 56 is driven by an actuator (not shown). When the bracket 56 a moves to the right side in the drawing along the guide rail 56 b by being driven by the actuator, the upper gripper 56 is pulled by the bracket 56 a. At this time, when the upper gripper 56 is pulled by the bracket 56 a, the upper gripper 56 mechanically interferes with a regulating member (not shown) and is lifted upward by this interference and pulled away from the lower gripper 57 (FIG. 4A). As a result, the grip of the sheet P by the upper gripper 56 and the lower gripper 57 is released, and the sheet P falls into the sheet tray 52. Then, the bracket 56 a and the upper gripper 56 move to the standby position (FIG. 4B).

Subsequently, in accordance with the discharge of the sheet P from the second discharge roller 51, the lower gripper 57 moves to the grip start position. Similarly, when the bracket 56 a moves to the left side in the drawing along the guide rail 56 b, the interference between the regulating member and the upper gripper 56 is released. The upper gripper 56 receives a biasing force from the biasing member and is pressed against the lower gripper 57 at the grip start position. As a result, the sheet P can be gripped between the upper gripper 56 and the lower gripper 57 (FIG. 3A).

As a result of such a series of operations, the gripper 55 can grip the sheet P discharged from the second discharge roller 51 to perform pull back operation to pull back the sheet P in the direction of the abutment plate 54.

The post-processing control part 70 controls the post-processing device 2. As the post-processing control part 70, a microcomputer mainly including a CPU, a ROM, a RAM, and an I/O interface can be used. The CPU performs various programs (processor). The ROM stores various programs to be performed by the CPU in the form of program codes readable by the CPU. The ROM stores data required for executing the program. The RAM is a memory serving as a work storage area. The program and the data stored in the ROM are read out by the CPU to be developed in the RAM. The CPU performs various processes on the basis of the program and data developed in the RAM.

In relation to one or more embodiments, when the post-processing control part 70 determines that a sheet bundle bound by a staple is discharged from the second discharge roller 51, the post-processing control part 70 performs the pull back operation on the sheet bundle.

FIG. 5 is a flowchart showing operation of the gripper 55 according to one or more embodiments. The processing shown in this flowchart is performed by the post-processing control part 70 each time the sheet P is discharged.

First, in step S10, the post-processing control part 70 determines whether the sheet P is discharged from the second discharge roller 51. This determination may be performed on the basis of the detection results of a sheet detection sensor 21 (see FIG. 1) disposed in the first conveyance path R1 or a sheet detection sensor 22 (see FIG. 1) disposed in the second conveyance path R2. When the sheet P is discharged from the second discharge roller 51, an affirmative determination is made in step S10, and the process proceeds to step S11. On the other hand, when the sheet P is not discharged from the second discharge roller 51, a negative determination is made in step S10 and the process returns to step S10.

In step S11, the post-processing control part 70 determines whether it is a first mode in which the sheet P is discharged from the second discharge roller 51 via the first conveyance path R1. This determination can be made on the basis of the detection results by the sheet detection sensor 21 or the sheet detection sensor 22. When it is the first mode, an affirmative determination is made in step S11, and the process proceeds to step S12. In this first mode, a single sheet P that has passed through the first conveyance path R1 is discharged from the second discharge roller 51. On the other hand, when it is the second mode in which the sheet bundle is discharged from the second discharge roller 51 via the second conveyance path R2, a negative determination is made in step S11, and the process proceeds to step S13.

In step S12, the post-processing control part 70 performs the pull back operation for the single sheet P. Specifically, the post-processing control part 70 controls the gripper 55 on the basis of the timing when the rear end of the sheet P is detected by the sheet detection sensor 21 disposed in the first conveyance path R1, the distance from the sheet detection sensor 21 to the second discharge roller 51, the conveyance speed of the sheet P, or the like, and performs the pull back operation on the sheet P discharged from the second discharge roller 51. By the execution of this pull back operation, the rear end of the sheet P discharged from the second discharge roller 51 is gripped by the gripper 55. Then, the gripper 55 pulls back the sheet P in the direction of the abutment plate 54, so that the rear end of the sheet P abuts against the abutment plate 54. When the rear end of the sheet P abuts against the abutment plate 54, the grip of the sheet P by the gripper 55 is released, and the sheet P is loaded on the sheet tray 52.

In step S13, the post-processing control part 70 determines whether the number of sheets to be bound of the sheet bundle is equal to or larger than the reference number of binding sheets. Since the sheet bundle with a smaller number of sheets to be bound becomes lightweight, when discharged from the second discharge roller 51, the sheet bundle jumps out largely. For this reason, there is a variation in the falling position of the sheet bundle, and unevenness tends to occur on the sheet tray 52. On the other hand, the sheet bundle with a larger number of sheets to be bound becomes heavier weight, when discharged from the second discharge roller 51, the sheet bundle does not jump out largely. Therefore, it is difficult for unevenness to occur on the sheet tray 52. The reference number of binding sheets is a reference value for separating a light weight sheet bundle which causes unevenness on the sheet tray 52 and a heavy weight sheet bundle such that unevenness is hard to occur on the sheet tray 52, and an optimum value is set through an experience or simulation (for example, twenty sheets). When the number of sheets to be bound of the sheet bundle is equal to or larger than the reference number of binding sheets, an affirmative determination is made in step S13, and the process proceeds to step S14. On the other hand, when the number of sheets to be bound of the sheet bundle is smaller than the reference number of binding sheets, a negative determination is made in step S13, and the process proceeds to step S15.

In step S14, the post-processing control part 70 does not perform the pull back operation. Therefore, the sheet bundle equal to or larger than the reference number of binding sheets is simply discharged from the second discharge roller 51 and loaded on the sheet tray 52.

In step S15, the post-processing control part 70 performs the pull back operation for a sheet bundle (a sheet bundle smaller than the reference number of binding sheets). Specifically, the post-processing control part 70 controls the gripper 55 on the basis of the timing when the rear end of the sheet bundle is detected by the sheet detection sensor 22 disposed in the second conveyance path R2, the distance from the sheet detection sensor 22 to the second discharge roller 51, the conveyance speed of the sheet P, or the like, and performs the pull back operation on the sheet bundle discharged from the second discharge roller 51. By the execution of this pull back operation, the rear end of the sheet bundle discharged from the second discharge roller 51 is gripped by the gripper 55. Then, the gripper 55 pulls back the sheet bundle in the direction of the abutment plate 54, so that the rear end of the sheet bundle abuts against the abutment plate 54. When the rear end of the sheet bundle abuts against the abutment plate 54, the grip of the sheet bundle by the gripper 55 is released, and the sheet bundle is loaded on the sheet tray 52.

As described above, according to one or more embodiments, the sheet discharge apparatus 50 includes: the second discharge roller (discharger) 51 that discharges the sheet P; the sheet tray (loading part) 52 on which the sheet P discharged from the second discharge roller 51 is loaded; the abutment plate (abutment member) 54 against which the rear end of the sheet P abuts so as to align the sheet P loaded on the sheet tray 52; the gripper (pull back member) 55 that performs pull back operation of contacting with the sheet P discharged from the second discharge roller 51 to pull back the sheet P in the direction of the abutment plate 54; and the control part (post-processing control part 70) that controls the gripper 55. When the post-processing control part 70 determines that a sheet bundle bound by a staple is discharged from the second discharge roller 51, the post-processing control part 70 performs the pull back operation on the sheet bundle.

According to this configuration, the sheet bundle discharged from the second discharge roller 51 is pulled back toward the abutment plate 54 by the gripper 55. As a result, the discharged sheet bundle can pass over the uppermost sheet bundle loaded on the sheet tray 52 and reach the abutment plate 54. As a result, it is possible to prevent each staple from being caught. As a result, it is possible to orderly load the sheet bundle on the sheet tray 52.

In one or more embodiments, when the number of sheets to be bound of the sheet bundle discharged from the second discharge roller 51 is equal to or larger than the reference number of binding sheets, the post-processing control part 70 does not perform the pull back operation on the sheet bundle.

According to this configuration, even when the sheet bundle is discharged from the second discharge roller 51, only when the number of sheets to be bound of the sheet bundle is smaller than the reference number of binding sheets, the pull back operation is performed on the sheet bundle. For a light weight sheet bundle, the amount of jumping out from the second discharge roller 51 is large, and the sheet bundle tends to be uneven. Therefore, when the pull back operation is performed only for a light weight sheet bundle, it is possible to orderly load the sheet bundle on the sheet tray 52. For a heavy weight sheet bundle, since the amount of jumping out from the second discharge roller 51 is small, the sheet bundle is hard to be uneven. Therefore, it is possible to orderly load the sheet bundle on the sheet tray 52 without performing the pull back operation on the sheet bundle.

In one or more embodiments, the gripper 55 contacts with both surfaces of the sheet bundle, and grips the sheet bundle. Specifically, the gripper 55 includes the upper gripper 56 that abuts against the uppermost sheet P of the sheet bundle and the lower gripper 57 that abuts against the sheet P on the lowermost surface of the sheet bundle.

According to this configuration, the gripper 55 can contact both surfaces of the sheet P to grip the sheet P so that the sheet P can be pulled back appropriately.

Hereinafter, the image forming apparatus according to one or more embodiments will be described. The difference from the image forming apparatus according to the previously-described embodiments is a method of controlling the gripper 55. Descriptions of the contents overlapping with those of the previously-described embodiments will be omitted, and the differences will be mainly described.

In one or more embodiments, the post-processing control part 70 controls the release timing when the gripper 55 releases the gripping after gripping the sheet P. Specifically, the post-processing control part 70 controls the release timing when the upper gripper 56 releases contact after contacting with the sheet P. The release timing of the upper gripper 56 can be controlled by adjusting the movement timing of moving the bracket 56 a to the standby position. If the movement timing for moving the bracket 56 a to the standby position is made to be earlier, the release timing of the upper gripper 56 can be made to be earlier.

FIG. 6 is a flowchart showing operation of the gripper 55 according to one or more embodiments. The processing shown in this flowchart is performed by the post-processing control part 70 each time the sheet P is discharged.

First, in step S20, the post-processing control part 70 determines whether the sheet P is discharged from the second discharge roller 51. When the sheet P is discharged from the second discharge roller 51, an affirmative determination is made in step S20, and the process proceeds to step S21. On the other hand, when the sheet P is not discharged from the second discharge roller 51, a negative determination is made in step S20 and the process returns to step S20.

In step S21, the post-processing control part 70 determines whether it is the first mode in which the sheet P is discharged from the second discharge roller 51 via the first conveyance path R1. When it is the first mode, an affirmative determination is made in step S21, and the process proceeds to step S22. In this first mode, a single sheet P that has passed through the first conveyance path R1 is discharged from the second discharge roller 51. On the other hand, when it is the second mode in which the sheet bundle is discharged from the second discharge roller 51 via the second conveyance path R2, a negative determination is made in step S21, and the process proceeds to step S23. In this second mode, a sheet bundle (a sheet bundle bound by the staple) having passed through the second conveyance path R2 is discharged from the second discharge roller 51.

In step S22, the post-processing control part 70 performs the pull back operation for the single sheet P. Specifically, the post-processing control part 70 controls the gripper 55 on the basis of the timing when the rear end of the sheet P is detected by the sheet detection sensor 21 disposed in the first conveyance path R1, the distance from the sheet detection sensor 21 to the second discharge roller 51, the conveyance speed of the sheet P, or the like, and performs the pull back operation on the sheet P discharged from the second discharge roller 51. By the execution of this pull back operation, the rear end of the sheet P discharged from the second discharge roller 51 is gripped by the gripper 55 and is pulled back to the direction of the abutment plate 54.

In the pull back operation of this step S22, the release timing of the upper gripper 56 is set so as to be after the usual release timing, that is, the timing when the rear end of the sheet P abuts against the abutment plate 54. Therefore, the rear end of the sheet P abuts against the abutment plate 54 while being gripped by the gripper 55. When the rear end of the sheet P abuts against the abutment plate 54, the grip of the sheet P by the gripper 55 is released, and the sheet P is loaded on the sheet tray 52.

In step S23, the post-processing control part 70 determines whether the number of sheets to be bound of the sheet bundle is equal to or larger than the reference number of binding sheets. When the rear end of the sheet bundle pulled back by the gripper 55 abuts against the abutment plate 54, the sheet bundle may be bounced back by the abutment plate 54. For this reason, the sheet bundle jumps out to the tip end side, and unevenness tends to occur on the sheet tray 52. This jumping out is more prominent as a sheet bundle is lighter in weight. On the other hand, since the amount of jumping out of a heavy weight sheet bundle is small, unevenness is hard to occur on the sheet tray 52. The reference number of binding sheets is a reference value for separating a light weight sheet bundle which causes unevenness on the sheet tray 52 due to the bouncing back by the abutment plate 54 and a heavy weight sheet bundle such that unevenness is hard to occur on the sheet tray 52, and an optimum value is set through an experience or simulation. When the number of sheets to be bound of the sheet bundle is equal to or larger than the reference number of binding sheets, an affirmative determination is made in step S23, and the process proceeds to step S24. On the other hand, when the number of sheets to be bound of the sheet bundle is smaller than the reference number of binding sheets, a negative determination is made in step S23, and the process proceeds to step S26.

In step S24, the post-processing control part 70 determines whether the number of sheets of the sheet bundle loaded on the sheet tray 52 is larger than the reference number of copies. As described above, when the rear end of the sheet bundle pulled back by the gripper 55 abuts against the abutment plate 54, the sheet bundle may be bounced back by the abutment plate 54. In particular, when the number of sheets of the sheet bundle loaded on the sheet tray 52 is large, the height of the rear end side of the sheet bundle is increased by the thickness of the staple, and the upper surface of the sheet bundle becomes closer to the horizontal state from the inclined state (see FIG. 7). Therefore, the jumping out described above becomes more prominent as the number of sheets of the sheet bundle loaded on the sheet tray 52 is larger. The reference number of copies is a reference value for separating the number of sheets of the sheet bundle which causes unevenness on the sheet tray 52 due to the bouncing back by the abutment plate 54 and the number of sheets of the sheet bundle such that unevenness is hard to occur on the sheet tray 52, and an optimum value is set through an experience or simulation. When the number of sheets of the sheet bundle is larger than the reference number of copies, an affirmative determination is made in step S24, and the process proceeds to step S26. On the other hand, when the number of sheets of the sheet bundle is equal to or less than the reference number of copies, a negative determination is made in step S24, and the process proceeds to step S25.

In step S25, the post-processing control part 70 performs the pull back operation for the sheet bundle. Specifically, the post-processing control part 70 controls the gripper 55 on the basis of the timing when the rear end of the sheet bundle is detected by the sheet detection sensor 22 disposed in the second conveyance path R2, the distance from the sheet detection sensor 22 to the second discharge roller 51, the conveyance speed of the sheet P, or the like, and performs the pull back operation on the sheet bundle discharged from the second discharge roller 51. By the execution of this pull back operation, the rear end of the sheet bundle discharged from the second discharge roller 51 is gripped by the gripper 55 and is pulled back to the direction of the abutment plate 54.

In the pull back operation of this step S25, the release timing of the upper gripper 56 is set so as to be after the usual release timing, that is, the timing when the rear end of the sheet bundle abuts against the abutment plate 54. Therefore, the rear end of the sheet bundle abuts against the abutment plate 54 while being gripped by the gripper 55. When the rear end of the sheet bundle abuts against the abutment plate 54, the gripping of the sheet bundle by the gripper 55 is released, and the sheet bundle is loaded on the sheet tray 52.

In step S26, the post-processing control part 70 performs the pull back operation for the sheet bundle. Specifically, the post-processing control part 70 controls the gripper 55 on the basis of the timing when the rear end of the sheet bundle is detected by the sheet detection sensor 22 disposed in the second conveyance path R2, the distance from the sheet detection sensor 22 to the second discharge roller 51, the conveyance speed of the sheet P, or the like, and performs the pull back operation on the sheet bundle discharged from the second discharge roller 51. By the execution of this pull back operation, the rear end of the sheet bundle discharged from the second discharge roller 51 is gripped by the gripper 55 and is pulled back to the direction of the abutment plate 54.

In the pull back operation of this step S26, the release timing of the upper gripper 56 is set so as to satisfy the following two requirements. The first requirement is that the release timing is after the timing when the staple of the sheet bundle pulled back by the gripper 55 passes the staple of the uppermost sheet bundle loaded on the sheet tray 52. The second requirement is that the release timing is before the timing when the rear end of the sheet bundle pulled back by the gripper 55 abuts against the abutment plate 54. The post-processing control part 70 releases the upper gripper 56 within a range that satisfies the above-mentioned two requirements, taking into consideration the rotational speed of the upper gripper 56 and the lower gripper 57 or the like. As a result, the upper gripper 56 is released before the rear end of the sheet bundle abuts against the abutment plate 54, and the gripping of the sheet bundle by the gripper 55 is also released. When the gripping of the gripper 55 is released, the sheet bundle cannot follow the rotational motion of the gripper 55. Therefore, the rear end of the sheet bundle abuts against the abutment plate 54 at a slower speed than the case where the rear end of the sheet bundle abuts against the abutment plate 54 while being gripped by the gripper 55.

As described above, according to one or more embodiments, the post-processing control part 70 can control the release timing when contact is released after the gripper 55 contacts with the sheet P. The post-processing control part 70 makes the release timing for the sheet bundle smaller than the reference number of binding sheets to be earlier than the release timing for the sheet bundle equal to or larger than the reference number of binding sheets.

According to this configuration, since the release timing of the gripper 55 is made to be earlier, the sheet bundle abuts the abutment plate 54 at a slower speed than the case where the sheet bundle abuts the abutment plate 54 while being gripped by the gripper 55. Thereby, it is possible to prevent the sheet bundle from being bounced back by the abutment plate 54. As a result, since unevenness is hard to occur on the sheet tray 52, it is possible to orderly load the sheet bundle on the sheet tray 52.

In one or more embodiments, whether the pull back operation with respect to the sheet bundle can be performed is determined on the basis of the number of sheets to be bound of the sheet bundle. However, in one or more embodiments, when the number of sheets of the sheet bundle loaded on the sheet tray 52 is large, the height of the rear end side of the sheet bundle is increased by the thickness of the staple, and the upper surface of the sheet bundle becomes closer to the horizontal state from the inclined state (see FIG. 7). For this reason, merely with discharge from the second discharge roller 51, the sheet bundle loaded on the sheet tray 52 tends to be uneven. Therefore, whether the pull back operation with respect to the sheet bundle can be performed may be determined on the basis of the number of sheets of the sheet bundle loaded on the sheet tray 52 instead of the number of sheets to be bound of the sheet bundle. In one or more embodiments, the release timing of the gripper 55 is switched by using the number of sheets to be bound of the sheet bundle and the number of sheets of the sheet bundle loaded on the sheet tray 52 as conditions. However, the release timing of the gripper 55 may be switched by using only one of the conditions.

Although the image forming apparatus and the sheet discharge apparatus according to one or more embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention.

For example, in one or more embodiments, the image forming apparatus includes an image forming apparatus main body that is responsible for an image forming function and a sheet processor that performs processing on a sheet. However, a sheet discharge apparatus may be applied to a sheet processor independent from the image forming apparatus.

Further, in one or more embodiments, the sheet processor includes a dedicated control part, and the control of the sheet discharge apparatus is performed by the control part. However, the sheet discharge apparatus may include a dedicated control part. When the sheet processor is combined with the image forming apparatus main body, the control part that controls the image forming apparatus main body may control the sheet discharge apparatus.

Although embodiments of the present invention have been described and illustrated in detail, the previously-described embodiments are made for purposes of illustration and example only and not limitation. The scope of the present invention should be interpreted by terms of the appended claims.

Although the disclosure has been described with respect to only a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that various other embodiments may be devised without departing from the scope of the present invention. Accordingly, the scope of the invention should be limited only by the attached claims. 

What is claimed is:
 1. A sheet discharge apparatus comprising: a discharger that discharges a sheet; a loading part on which the sheet discharged from the discharger is loaded; an abutment member that abuts against a rear end of the sheet in a direction of discharging to align the sheet loaded on the loading part; a pull-back member that performs a pull-back operation by contacting with the sheet discharged from the discharger to pull back the sheet toward the abutment member; and a hardware processor that controls the pull-back member, wherein the hardware processor performs the pull-pack operation on a sheet bundle upon determining that the sheet bundle bound by a binder is discharged from the discharger.
 2. The sheet discharge apparatus according to claim 1, wherein, upon determining that the sheet bundle is discharged from the discharger, the hardware processor determines whether the pull-pack operation is performed on the sheet bundle based on a number of sheets of the sheet bundle loaded on the loading part, or a number of the sheets to be bound of the sheet bundle discharged from the discharger.
 3. The sheet discharge apparatus according to claim 2, wherein, when the number of sheets to be bound of the sheet bundle discharged from the discharger is equal to or larger than a reference number of binding sheets, the hardware processor determines not to perform the pull-pack operation on the sheet bundle.
 4. The sheet discharge apparatus according to claim 2, wherein, when the number of sheets of the sheet bundle loaded on the loading part is larger than a reference number of copies, the hardware processor performs the pull-pack operation on the sheet bundle discharged from the discharger.
 5. The sheet discharge apparatus according to claim 1, wherein the hardware processor controls a release timing of when the pull-pack member releases the sheet, and the release timing for the sheet bundle in a case where a number of binding sheets is smaller than a reference number is earlier than the release timing for the sheet bundle in a case where a number of binding sheets is equal to or larger than the reference number of binding sheets.
 6. The sheet discharge apparatus according to claim 1, wherein the pull-pack member is a gripper that contacts with both surfaces of the sheet bundle to grip the sheet bundle.
 7. The sheet discharge apparatus according to claim 6, wherein the gripper comprises an upper gripper that abuts against the uppermost surface of the sheet bundle and a lower gripper that abuts against the lowermost surface of the sheet bundle.
 8. An image forming apparatus comprising: an image forming apparatus main body that forms an image on a sheet; a sheet processor that applies processing to the sheet fed from the image forming apparatus main body; and a hardware processor that controls the sheet processor, wherein the sheet processor comprises a sheet discharge apparatus that discharges the sheet, the sheet discharge apparatus comprises: a discharger that discharges the sheet; a loading part on which the sheet discharged from the discharger is loaded; an abutment member that abuts against a rear end of the sheet in a direction of discharging to align the sheet loaded on the loading part; and a pull-pack member that performs a pull-pack operation by contacting with the sheet discharged from the discharger to pull back the sheet toward the abutment member, and the hardware processor performs the pull-pack operation on a sheet bundle upon determining that the sheet bundle bound by a binder is discharged from the discharger.
 9. The image forming apparatus according to claim 8, wherein the sheet processor further comprises a binding processor that binds a plurality of the sheet with the binder to create the sheet bundle. 